1. Field of the Invention
The present invention generally relates to a system and a method for providing a location service, and more particularly to a system and a method for providing a location service that can provide a deferred location request service.
2. Description of the Related Art
With the increase in demand for various location-related services based on location, various location services using the location of a mobile terminal are being provided and development for the expansion of location services is being accomplished. The expansion of location services will be the basis of a 4G communication service.
Recently, a deferred location request service or a triggered location request service is being provided as a location service. A deferred location request service refers to a service for establishing preset criteria, periodically or non-periodically computing the position estimates of a Secure User Plane Location (SUPL) Enabled Terminal (SET), and providing an SUPL AGENT with occurrence of a corresponding event when the position estimates of the SET satisfies the preset criteria.
A conventional method for providing deferred location request service information will be described with reference to FIG. 1 illustrating a method for providing a deferred location request service according to the prior art. A SUPL AGENT 10 transmits a Mobile Location Protocol Triggered Location Reporting Request (MLP TLRR) message, thereby requesting a Home-SUPL Location Platform (H-SLP) 20 to provide a deferred location request service in step 102.
If the MLP TLRR message is received from the SUPL AGENT 10, the H-SLP 20 determines the routing information of a corresponding target SET 30 in step 104. That is, the H-SLP 20 determines if the target SET 30 is in a roaming state and uses a SUPL.
If the target SET 30 is not in a roaming state and uses the SUPL, i.e. a location service, the H-SLP 20 transmits a SUPL Initiation (INIT) message to the target SET 30 and starts the deferred location request service in step 106. The SUPL INIT message includes a SESSION_ID, which is an identification (ID) for identifying message exchanges between the H-SLP 20 and the target SET 30, a Position (POS) method representing a positioning method, and criteria used for determining if an event has occurred.
If the SUPL INIT message is received from the H-SLP 20, the target SET 30 determines if the target SET 30 is currently connected to a packet data network in step 108. If the target SET 30 is not currently connected to the packet data network, the target SET 30 attempts a connection to the packet data network.
After performing a network connection with the H-SLP 20, the target SET 30 transmits a SUPL POS INIT message to the H-SLP 20 in step 110. The SUPL POS INIT message includes a SESSION_ID, which is an ID for identifying message exchanges between the H-SLP 20 and the target SET 30, a LOCATION_ID representing information about a network including the target SET 30, a NETWORK_ID, a SYSTEM_ID, and a SET_CAPABILITY representing positioning capability.
If the SUPL POS INIT message is received from the target SET 30, the H-SLP 20 compares the SET_CAPABILITY included in the SUPL POS INIT message with its own location measurement capability, thereby determining a POS METHOD. Further, the H-SLP 20 and the target SET 30 perform positioning according to the determined POS method in step 112.
After performing the positioning, the target SET 30 compares its own position estimates with the event occurrence criteria included in the SUPL INIT message, and determines if an event requested by the SUPL AGENT 10 has occurred. As a result of the determination, if the event has occurred, the target SET 30 reports the occurrence of the event to the H-SLP 20 by using a SUPL DEFERRED_REPORT message in step 114. The SUPL DEFERRED_REPORT message includes a SESSION_ID, a CLIENT_ID, and a POS_ESTIMATE representing the computed position estimates of the target SET 30.
If the SUPL DEFERRED_REPORT message is received from the target SET 30, the H-SLP 20 reports the occurrence of the event to the SUPL AGENT 10 by using an MLP Triggered Location Report (TLR) message in step 116. The MLP TLR message includes a REQ_ID for identifying the deferred location request service, and a TLR_POS representing the computed position estimates of the target SET 30.
After reporting the occurrence of the event, if the deferred location request service is being provided, the target SET 30 transmits a SUPL DEFERRED START message for subsequent positioning to the H-SLP 20 by using the event occurrence criteria included in the SUPL INIT message, thereby requesting the start of a new positioning procedure in step 117.
If the SUPL DEFERRED START message is received from the target SET 30, the H-SLP 20 performs a subsequent positioning procedure of the target SET 30 in step 118. The target SET 30 compares its own position estimates with the event occurrence criteria included in the SUPL INIT message, and determines if the event requested by the SUPL AGENT 10 has occurred.
If the event has occurred, the target SET 30 reports the occurrence of the event to the H-SLP 20 by using the SUPL DEFERRED_REPORT message in step 120. If the SUPL DEFERRED_REPORT message is received from the target SET 30, the H-SLP 20 reports the occurrence of the event to the SUPL AGENT 10 by using the MLP TLR message in step 122. Further, the target SET 30 and the H-SLP 20 repeat steps 117, 118, 120 and 122 until a preset end time is reached. If the preset end time is reached, the procedure for providing the deferred location request service information is terminated.
The conventional method for providing the deferred location request service information as described above repeats a series of steps of: first computing the position estimates of a SET; comparing the computed position estimates with corresponding criteria; and determining if an event requested by a SUPL AGENT has occurred, and reporting the results of the determination.
In the conventional method as described above, since the required position estimates of a SET must be newly computed whenever the occurrence or non-occurrence of an event is determined, the whole process is complicated due to the repetitive positioning. Further, the conventional method is inefficient because the computed position estimates of the set or assistant data for computing the position estimates are used only once for determining if a corresponding event has occurred even when it can be reused for determining if a subsequent event has occurred.